We explored the effect of N addition and adult canopy competition on the recruitment of lost preferred species in the Patagonian steppe, where a decelerated N cycling scenario (sensu Ritchie et al., 1998) had been previously detected. In the first experiment we demonstrated that the preferred scarce grass Bromus pictus has typical traits of Competitive species, while the dominant less preferred Pappostipa speciosa has typical traits of Stress tolerant species (sensu Grime, 1997): B. pictus showed higher maximum Relative Growth Rate, water consumption and competitive ability than P. speciosa. In the second experiment, we proved that without N addition, seedlings of the preferred species showed its maximum survival rate under moderate grazing, where adult competition is lower than under ungrazed conditions and N-limitation is lower than under intense grazing. Instead, with N addition, the survival rate of B. pictus was maximum under intense grazing, where N limitation is maximum and adult competition is minimum. These results suggest that in degraded systems subjected to a decelerating N cycling scenario, the revegetation with preferred species would require recovering soil N levels, and would be more successful in the most degraded sites, where the remnant canopy has low cover.

我们探索了氮的添加和成年冠层竞争对巴塔哥尼亚草原失踪的首选物种的募集的影响，在巴塔哥尼亚草原中，先前已检测到减速的N循环场景（sensu Ritchie等人，1998）。在第一个实验中，我们证明了偏爱的稀有草布鲁姆斯具有典型的竞争性状，而优势次之的不受欢迎的番木瓜具有耐压性状的典型性状（sensu Grime，1997）：毕赤比目鱼显示出更高的最大相对生长率。 ，水的消耗和竞争能力要比P. speciosa高。在第二个实验中，我们证明了不添加N的情况下，优选物种的幼苗在中等放牧条件下表现出最大的成活率，成年人的竞争程度低于未放牧条件下的成年竞争，而氮极限低于激烈放牧条件下的成年竞争。取而代之的是，添加N后，在激烈的放牧条件下，小菜蛾的存活率最高，其中N限制最大，成年竞争最小。这些结果表明，在退化的系统中，氮循环降低的情况下，优选物种的植被恢复将需要恢复土壤中的氮含量，而在退化程度最高的地方，其剩余冠层的覆盖率较低，这将更加成功。